This invention relates to an optical recording apparatus for writing information on an optical recording medium by a radiation beam, and in particular to a method for setting an optimum write power level of the radiation beam. The method includes: writing a series of test patterns on the recording medium, each pattern with a different value of the write power level, reading the patterns to form corresponding read signals, deriving a value of a read parameter from each read signal, and fitting to a curve the values of the read parameter to obtain a function defining a relation between the write power level and the read parameter. The invention further relates to an apparatus for writing information on an optical recording medium, including a radiation source for emitting a radiation beam having a controllable write power level, a control unit for writing a series of test patterns, each pattern with a different value of the write power level, a read unit for reading the patterns and forming corresponding read signals, a first processor for deriving a value of a read parameter from each read signal, a second processor for fitting to a curve the values of the read parameter to a function defining a relation between the write parameter and the read parameter.
A processor may be of an analog or digital type and includes programmable processors and fixed-program processors. The processor may include memory means and an arithmetic unit.
A recording method according to the preamble is known from the U.S. Pat. No. 5,185,733 hereby incorporated in whole by reference. In this method, a series of test patterns is written on the medium, each subsequent test pattern being written with an increased write power level. After reading the written patterns, a curve fitting algorithm fits a second order polynomial to the amplitudes of the read signal of each pattern as a function of the write power level. The write power corresponding to the maximum of the polynomial is selected as the optimum write power for subsequently recording information of the medium. The problem of the noise character of the read signal is mitigated by curve-fitting.